共查询到20条相似文献,搜索用时 0 毫秒
1.
Local as well as surface waves excited in a streamingless plasma are investigated. In addition to the gradient instabilities of an isothermal plasma now branches of a convective type are found in plasmas with a hot electron componentZ T
e
T
i
. Both their frequencies and growth rates may exceed the ion cyclotron frequency, >
Bi
even if the effect of the finite ion Larmor radius is negligible. Then the surface waves may become of enhanced importance. We compare, therefore, the conditions for excitation and the growth rates of the surface waves with those of the short wavelength (local) perturbations. Upper estimates of the saturated wave amplitudes are also given. For a special profile of the plasma density the problem is solved analytically also in the plasma boundary layer.On leave of absence from the Physical and Technical Institute, Kharkov, U.S.S.R. 相似文献
2.
3.
An analytical solution of the nonlinear dynamic equations for a galactic disk is found. This solution describes the spiral design of spiral galaxies. The logarithmic profile of the spiral design and relatively larger density fluctuations as compared to velocity-field fluctuations are explained. Breaking of the obtained solution takes place for a certain critical amplitude. This can be a mechanism for the formation of galactic shocks and narrow star formation regions. 相似文献
4.
5.
Nonlinear effects stabilizing the convective instabilities excited in an anisothermic plasma (T
etT
i) at the plasma boundaryaVs/
Bi) are discussed. Waves having in the linear theory (Part I) the highest growth rates (
Bi) saturate at first. Being excited by a small part of slow plasma electrons (
zTe) only, they saturate at a relatively low level. Further, surface waves with lower frequencies and higher phase velocities (
ph/kz) become dominant and a broadening of the plasma boundary occurs. For their saturation nonlinear interaction is more important than the quasilinear effects. During the time interval of several
Bi
–1
the longest surface waves withk
yBi/Vs, BikyVs and
ph
Te
saturate at the absolutely highest level. The plasma boundary broadens in the meanwhile up toaV
s/Bi. The wave energy is comparable to the whole energy connected with the longitudinal motion of the initially thermal electrons inside this boundary layer. The wave amplitude is large enough to trap the initially cold ions belonging to this layer and heat them up to energies comparable to those of the electron component. The heating process occurs again within several
Bi
–1
and the Larmor radius of the ions is then comparable toV
s/Bi. Further evolution of the system is governed by the unstable local perturbations.He leaves of absence from thePhysical and Technical Institute, Kharkov, USSR. 相似文献
6.
We studied synchronization behaviours of spiral waves in a two-layer
coupled inhomogeneous excitable system. It was found that phase
synchronization can be observed under weak coupling strength. By
increasing the coupling strength, the synchronization is broken
down. With the further increase of the coupling strength, complete
synchronization and phase synchronization occur again. We also found
that the inhomogeneity in excitable systems is helpful to the
synchronization. 相似文献
7.
The effect of physiological and pathological abnormal excitation of a myocyte on the spiral waves is investigated based on the cellular automaton model. When the excitability of the medium is high enough, the physiological abnormal excitation causes the spiral wave to meander irregularly and slowly. When the excitability of the medium is low enough,the physiological abnormal excitation leads to a new stable spiral wave. On the other hand, the pathological abnormal excitation destroys the spiral wave and results in the spatiotemporal chaos, which agrees with the clinical conclusion that the early after depolarization is the pro-arrhythmic mechanism of some anti-arrhythmic drugs. The mechanisms underlying these phenomena are analyzed. 相似文献
8.
本文探讨具有温度和密度梯度的非均匀量子等离子体系统, 获得了该系统在离子与中子碰撞频率较低情况下的二维非线性流体动力学方程. 求得了非均匀量子等离子体中的电势的冲击、爆炸和旋涡解.分析讨论了在致密天体物理环境中静电势的变化, 结果表明电势的冲击波的幅度和爆炸波的宽度,都随密度的增大(即随无维量子参量的减小)而增大, 但随漂移速度的增大(即随密度和温度梯度的增大)而减小; 静电势随时空相位的增大而趋向于稳定值, 系统最后达到稳定的状态. 旋涡解表明,旋涡静电势的时空分布呈现稳定的周期性的旋涡流. 相似文献
9.
10.
11.
12.
The Vlasov kinetic equation is solved using gyrokinetic theory and the dielectric tensor for non-relativistic, magnetized, bi-Maxwellian plasmas is calculated. A generalized dispersion relation for kinetic Alfven waves is derived taking into account the density inhomogeneity and temperature anisotropy. The modified dispersion relation thus obtained is then used to examine the propagation characteristics of the kinetic Alfven waves in the inertial regime. The importance of density inhomogeneity and temperature anisotropy for Solar corona is highlighted. The growth rate of the inertial Alfven wave proves that density inhomogeneity acts as a source of free energy. 相似文献
13.
14.
In the injection of electron-Bernstein waves (EBW) into a plasma, proposed for plasma heating and current drive in over-dense plasma, conversion of the fundamental to its second harmonic is predicted analytically and observed in computations. The mechanism is traced to the existence of locations where one can have both wave number and frequency matching between the fundamental and its harmonic. Further, at such locations, the second harmonic commonly has minimal group velocity, and this allows the amplitude of the second harmonic to build to values exceeding that of the fundamental at power levels less than anticipated in experiments. The second-harmonic power can then be deposited at half-harmonic resonances of the original wave, often far from the desired location of energy deposition. Estimates for the power at which this is significant are given. 相似文献
15.
The Landau damping behavior in a cylindrical inhomogeneous warm magnetized plasma waveguide has been studied.The radial inhomogeneity for different characteristic lengths(L0) with strong spatial dispersion has been taken into account.The analyses have been considered for two limits ωce ωpe and ωce ωpe. Due to the radial inhomogeneity of the plasma, all essential equations for studying the Landau damping are calculated in the Bessel–Furrier and differential Bessel–Furrier expansions. The dependence of Landau damping on the inhomogeneity, temperature and external magnetic field for electrostatic modes is scrutinized and described in detail through numerical calculations. The associated numerical results are presented and discussed. 相似文献
16.
17.
《Optics Communications》1980,34(1):43-45
Based on the vector wave equations of an inhomogeneous circular waveguide, asymptotic eigenvalues of the system of the coupled second-order differential equations are given, of which the first-order eigenvalues coincide with the well-known WKB solutions. A parabolic-index optical fiber is examined to obtain the propagation constants. These asymptotic results are compared with the perturbational solutions and both are shown to be in agreement. 相似文献
18.
N. S. Bellyustin 《Radiophysics and Quantum Electronics》1978,21(11):1087-1093
In this paper we discuss an asymptotic method which permits one to separate the initial equations for the fields in a plane stratified plasma into two independent systems, describing waves of differing types which propagate in a single direction. The coefficients of the derived equations remain regular at points of equality between the indices of refraction of normal waves, n1=n2. The equations are used to analyze a specific type of interaction which is of current interest in connection with research on low-frequency waves in the ionosphere. A solution is found by the method of the standard system which describes the field in the interaction region; outside this region, it turns into the geometric optics solution. Wave transformation coefficients are compared with those obtained earlier by the phase integral method.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 21, No. 11, pp. 1563–1571, November, 1978.The author thanks N. G. Denisov for constant interest in this work and helpful discussions, and V. E. Belov and L. V. Rodygin for a valuable remark. 相似文献
19.
20.
We analyse the interaction of a relativistic electron with a uniform magnetic field in the spiral dislocation spacetime.We show that analytical solutions to the Dirac equation can be obtained,where the spectrum of energy corresponds to the relativistic Landau levels.We also analyse the influence of the spiral dislocation on the relativistic Landau levels by showing that there exists an analogue of the Aharonov–Bohm effect for bound states. 相似文献